Choosing the right pump for your paint application means deciding which materials of construction, design, and size are right for your fluid and process. With so many different pump options, and so many different paint characteristics to consider, it can be hard to find just the right pump to employ. When making your selection, consider the following.
Typical Paint Pumping Conditions
Generally speaking, paints are handled and pumped within these parameters:
- Flow rates can vary from one gallon per minute to several hundred gallons per minute
- temperatures are usually ambient or at least under 125 F
- Pressures are generally 100 PSI or less
- Suction is normally flooded
- Viscosity varies from a few hundred SSU to 25,000 SSU and higher
- Duty cycles range from occasional transfer to 24 hours per day recirculation
Materials of Construction Considerations
Pump construction varies widely depending primarily on the amount of abrasives, the type of paint, solvents used, and the cleaning cycle.
Nonabrasive or Mildly Abrasive Paints
For the nonabrasive or mildly abrasive paints, e.g., varnish or enamel, standard or steel fitted pumps with bronze or carbon graphite bushings and Teflon packing are a good first consideration. If the system is to be flushed with solvent, carbon graphite bushings are preferred.
Mechanical seals are seldom used for handling paint because of the problems caused by abrasives and solvents.
Moderately Abrasive Paints
For the moderately abrasive paints, e.g., primers and some with oxide pigments, consider a pump with cast iron idler and rotor or steel fitted construction with hardened steel idler and rotor. Some Viking Pumps, for example, are fitted with a ceramic idler bushing, an abrasion resistant idler pin, and a mechanical seal with ceramic on ceramic faces.
The effects of the paint or cleanup solvents on the Viton secondary sealing elements must be considered. Abrasive liquid seals with secondary sealing elements of materials other than Viton are available. For the unusually abrasive paints such as red iron oxide primer, consider other specialized features like tungsten carbide idler pin, flush over the mechanical seal, or a special drive for the seal.
Reduced speeds and pressures must also be considered when handling the extremely abrasive paints.
Latex paints are not quite as sensitive to handling as the latex emulsions since the paints have pigments, additive, and additional water in them. Stainless pumps are often considered for water base or latex paints, particularly where the system is flushed with water. These constructions are also used when nonsparking materials are requested.
Protecting Your Pumps
On a system where there is a possibility of the discharge line being closed while the pump is running, precautions should be made for protecting the equipment from excessive pressure build-up.
Consider using a safety relief valve on the pump or in the line. This works well, except when handling paints that build up or settle out, potentially clogging the valve and rendering the safety relief valve inoperative. In cases like this, a coupling with overload protection or some similar protection afforded by the drive should be considered.
Need help selecting the right pump for your process? Ask us about it! We gladly provide technical assistance to businesses and municipalities in Wisconsin and upper Michigan!